The present invention refers to a forming press especially suitable for effecting perimetral bends on rectangular sheets in order to produce panels with edges bent one or more times on all four sides.
In particular, the forming press according to this invention is of the type essentially comprised of a support structure having a C cross section with horizontal arms, a fixed lower counterblade and an upper blank holder counterblade, movable in the vertical direction, the said counterblade being supported and extending longitudinally with respect to the said support structure, a cutter block carriage movably guided in the vertical direction between the arms of the said support structure, an upper bending blade and a lower bending blade both mounted on the said cutter block and cooperating with the said counterblades for the bending, respectively downward and upward, of the edge of a plate firmly held by the counterblades themselves. Such a forming press comprises the basic component of the machine for the production of plate panels with bent edges, described in the U.S. patent application Ser. No. 941,988, filed on Sept. 13, 1978 in the name of the same applicant now U.S. Pat. No. 4,242,898 and cited here for reference.
Relative to the bending of plates, e.g., the perimetral bending of a plate in order to obtain an appropriate panel with bent edges, there is a recognized technical problem when the plate has one or both of the surfaces treated, e.g., satinized, prepainted, or having any other similar protective coating.
This problem consists in the fact that during the bending process substantial and sudden stresses are generated; they are localized along the line of bending of the plate. Such stresses induce stretching effects in the film-like coating layers and cause a definite weakening of the said layers with the possibility of laceration, microfissuring, more or less substantial and more or less diffuse cracks, but always unacceptable in the finished product. In the case of plates with satinized (or similarly treated) surfaces, the elimination of the satiny appearance of the plate itself is generally observed along the bending line.
A resolution of this problem is particularly desirable in the production of panels destinated, e.g., for the manufacture of metal furniture, refrigerators, washing machines, radiators, convectors, shelving in general, and the like, where the possibility of bending surface-treated plates without incurring the above inconveniences would eliminate a whole series of operations and treatments that have been necessary to date with regard to the finished product and thus would result in substantial production savings.
The main purposes of this invention is to resolve the above technical problem by offering a forming press of the type defined above that would have structural and functional characteristics such that one or more bends could be effected along one or more sides of a rectangular plate having one or both surfaces pretreated, e.g., prepainted or satinized.